1. Technical Field
This invention applies generally to the field of pneumatically operated tools and more specifically to pneumatically operated tool for removal and application tire chain cross chain links.
2. Background of the Invention
Tire chains, used by a variety of vehicles including large over the road freight trucks and tractors, and other assorted vehicles and equipment often times use tire chains to increase traction. A tire chain is made up of a pair of side chain assemblies which are connected by cross chains. One side chain assembly is fitted facing each of the tire inner wall and the tire outer wall. The cross chains lay across the tread of the tire and are attached at either of its two ends to the side chain assemblies and therefore come in contact with the road or other surface as the tire rotates thereby increasing the vehicle's traction. Since the cross chains are the component of the tire chain which comes in contact with the ground or other road surface, they are the most likely to fail. Therefore, a means for removal and reapplication of cross chains is needed.
More often than not, cross chains fail during use and often times, the vehicle employing the tire chains is at a location distant from the availability of repair services. Therefor, the tool or other apparatus for removal and application of tire cross chains had to be readily deployable at such locations. Because a substantial amount of force is required to open the hooks on the tire cross chains for removal and a similar force or pressure is required to close the hooks on the new chains, a source of power is required to provide such pressure.
De Boer, U. S. Pat. No. 4,261,090 discloses a tire cross chain applying and removing apparatus having a pneumatic diaphragm motor which operates two pairs of fixed and moveable jaws for opening the hooks on tire cross chains for removal from the side chains and for closing the hooks on new cross chains for applying to the side chains. Power for the tool is provided by pneumatic pressure from a vehicle air pressure system. The De Boer apparatus comprises a stand for supporting the pneumatic diaphragm motor having a shank fixed on the stand. The stand has a pair of movable jaw members pivotally mounted thereto. The jaws are operated by a reciprocal rod pivotally connected to the pair of moveable jaws, the reciprocal rod being actuated by the pneumatic diaphragm motor. The De Boer invention resides in a pair of double jaws actuated by a pneumatic diaphragm motor, one pair of jaws being formed to fit within a hook of a cross chain to open the hook, the other pair of jaws forming clamping jaws to close a hook on the new cross chain. The jaws are mounted on the support which carries a pneumatic diaphragm motor for actuating the jaws. Connection to a vehicle air pressure system enables the apparatus to be operated at remote locations. The De Boer apparatus includes a manually operated valve which is connected to an air line which extends through the tool's handle to the pneumatic diaphragm motor.
The manually operated valve of the De Boer apparatus is a single action valve which allows air pressure through the valve to the pneumatic diaphragm motor upon operation of the valves actuator button. Upon release of the button, air pressure is bled back through the air line resulting in a extremely slow release or recovery of the jaws to an open position.
What is needed is a tool for removing tire cross chains for connection to a pneumatic power source having a manually operated valve or regulator which directs air to the first side of the pneumatic diaphragm motor for actuating the jaws in a first direction causing the jaws to close and which, when the manually operated valve or regulator is released deactivating the valve, allows the air against the diaphragm to bleed back through the valve to a bleed port allowing a much faster recovery of the jaws for opening. There exist advantages to such a design both in terms of basic functionality as well as from a safety standpoint.
The De Boer apparatus is also constructed having the single extended shank which extends from the support for the pneumatic diaphragm motor, for attachment of the pair of moveable jaws. Because of the force and torque generated by the tool in operation, the extended shank has a tendency to twist against the stand and the pneumatic diaphragm motor. What is needed is a more substantial jaw assembly which eliminates the propensity of the fixed jaw to torque at the connection to the pneumatic diaphragm motor.